Energy harvesting device manufactured by print forming processes

ABSTRACT

Embodiments of making an energy harvesting device are described. In one embodiment, a case and integrated piezoelectric cantilever to harvest vibration energy from an environment being sensed is produced via a print forming method injection molding method. The cantilever device consists of a piezoelectric material member, and a proof mass of high density material coupled to the piezoelectric member. The print forming method is used to build up the base and walls of the device as well as the neutral layers of the piezoelectric member. Metal layers are printed to form the electrode layers of the piezoelectric member and the electrical contact portions of the device. Passive components can also be formed as part of the layers of the device. The entire assembly can be encapsulated in plastic.

FIELD

Embodiments of the invention relate generally to miniaturized electricalsystems, and specifically to devices for harvesting energy.

BACKGROUND

The use of miniaturized electrical systems (Microsystems) on the orderof 1 cm² has been proposed to provide distributed sensing capability.Microsystem sensors can be used to monitor various environmental andoperational conditions and transmit signals back to a host receiver formany different applications, such as industrial monitoring, securityapplications, weather prediction, and so on. The design andimplementation of such devices and systems requires overcoming severalchallenges, such as designing small and robust packaging and providingadequate transmitter power. A major consideration in designing suchsystems remains providing adequate electrical power, and for manyMicrosystems, this challenge remains a significant obstacle. In general,current miniature battery technologies cannot store enough energy topower these systems for long periods of time, such as on the order ofmonths. Another disadvantage of battery use is that many sensorapplications involve harsh or limited access environments that can limitor disable battery performance and/or render battery maintenancevirtually impossible.

One approach to overcome the problem of providing enough battery powerfor microsystems is to extract energy from the surrounding environment.This approach, which is called energy harvesting (or scavenging)eliminates the need for an external or stored power supply, thusallowing a system to be made fully autonomous, that is, one thatrequires no external power connections or maintenance. As long as thesource of environmental energy is available, an energy harvestingmicrosystem can remained fully powered, virtually non-stop, whileproviding information to the user.

Several techniques have been proposed and developed to extract energyfrom the environment. The most common available sources of energy arevibration, temperature, and stress (pressure). In many environmentalapplications, vibration energy may be the most readily available andeasiest to convert into electricity. In general, vibration energy can beconverted into electrical energy using one of three techniques:electrostatic charge, magnetic fields, and piezoelectric materials.Piezoelectric generation of electricity from vibration energy typicallyrepresents the most cost-effective approach, as the electrostatic andmagnetic techniques usually require more extensive design, packaging,and integration work to adapt to particular applications.

Current methods of manufacturing small piezoelectric energy harvestingdevices typically involve traditional PC (printed circuit) boardtechniques in which components are mounted on a PC and then integratedinto a separate housing or other structure. Such methods are typicallyexpensive and inefficient when small-scale devices are produced.Moreover, for applications in which vibration energy is converted toelectrical energy, a rigid platform for the piezoelectric elements mustbe provided to maximize energy generation. Present methods ofpiezoelectric device manufacture typically involve mounting or attachinga piezoelectric beam to a separate case. Even if the bond between thecase and beam is strong, the attachment point often represents a sourceof energy loss due to vibrational transmission and/or losses in theinterface region.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of exampleand not limitation in the figures of the accompanying drawings, in whichlike references indicate similar elements and in which:

FIG. 1 illustrates vibration energy, such as in a rotating tire that canbe used in an energy harvesting device according to an embodiment.

FIG. 2A illustrates a piezoelectric bimorph for use in an energyharvesting device, according to an embodiment.

FIG. 2B illustrates the piezoelectric bimorph of FIG. 2A under atransverse loading.

FIG. 3 illustrates a cut-away view of an energy harvesting devicemanufactured by a print-forming process, according to an embodiment.

FIG. 4 is a flowchart that illustrates a method of manufacturing aprint-formed energy harvesting device, according to an embodiment.

FIG. 5 illustrates a carrier or substrate upon which a ceramic substrateand surface mount pads have been printed, under an embodiment.

FIG. 6 illustrates the formation of walls upon the substrate of FIG. 5.

FIG. 7, which illustrates the deposition of a ceramic layer of apiezoelectric cantilever beam of FIG. 6.

FIG. 8 illustrates the formation of the second electrode on thecantilever beam of FIG. 7.

FIG. 9 illustrates the formation of the third electrode on thecantilever beam of FIG. 8.

FIG. 10 illustrates the deposition of rim layers and sacrificial inkmaterial over the cantilever beam of FIG. 9.

FIG. 11 illustrates the formation of a lid on the rim structure of FIG.10.

FIG. 12A illustrates an energy harvesting device with a proof massformed within a case for integration with passive electronic components.

FIG. 12B illustrates the deposition of a proof mass through a printforming method, under an embodiment.

FIG. 12C illustrates the formation of an electrode layer of a cantileverbeam with the proof mass formed as shown in FIG. 12B.

FIG. 12D illustrates the formation of a PZT layer of a cantilever beamwith the proof mass formed as shown in FIG. 12B.

FIG. 13 illustrates the energy harvesting device of FIG. 12A with afirst layer of passive components.

FIG. 14 illustrates the energy harvesting device of FIG. 13 with asecond layer of passive components.

FIG. 15 illustrates the energy harvesting device of FIG. 14 with a toplayer of electrical components.

FIG. 16 illustrates a power harvesting device and sensor/transmittercircuit of an intelligent tire system, under an embodiment.

DETAILED DESCRIPTION

Embodiments of an energy harvesting device manufactured throughprint-forming methods are described. In one embodiment, a screenprinting process, or similar print-forming technology is used to producean energy harvesting device that can be used to power small-scale sensorcircuits, such as a tire pressure monitoring system or similar systems.The print-forming process involves adding successive layers of differentscreen printed materials to a substrate to build the device. After thedevice has been formed by the printing process, it is fired or cured toform a finished product. In one embodiment, a piezoelectric cantileveris incorporated within the screen printed structure to form the energyharvesting segment of the device. The piezoelectric cantilever can be abimorph or multimorph cantilevered beam (or other similar structure)that vibrates under an externally applied load. This cantilever issurrounded by an external shell (package) of a material, such as ceramicthat provides the multiple roles of: electrical interconnect,environmental shielding, and over-travel protection. Such a device canbe used to provide power to sensor systems deployed in various vibrationintensive environments, such as tire pressure monitoring systems,seismic systems, and the like.

In the following description, numerous specific details are introducedto provide a thorough understanding of, and enabling description for,embodiments of a print-forming manufactured energy harvesting device.One skilled in the relevant art, however, will recognize that theseembodiments can be practiced without one or more of the specificdetails, or with other components, systems, and so on. In otherinstances, well-known structures or operations are not shown, or are notdescribed in detail, to avoid obscuring aspects of the disclosedembodiments.

Microsystem sensors can be used in a variety of different environmentsto provide signals that represent one or more characteristics orparameters of the environment being sensed. One critical considerationin the installation of microsystems is providing power to the sensor.Many environments in which microsystem sensors are deployed eitherproduce or are subject to vibrations. In one embodiment, an energyharvesting device uses vibration energy present in an environment beingsensed to produce electricity to power the sensor.

Automotive applications represent one field where vibration energy frommotion of the vehicle in use is readily present and can be used toprovide power to sensor networks in a car. In one embodiment, an energyharvesting device is used in a tire pressure sensing module that isdeployed inside of an automobile, truck or other vehicle or machine tireto sense the air pressure inside of the tire and transmit the airpressure information to a control or processor module that can reportlow or abnormal tire pressures. The rubber carcass of a tire as it rollsalong a surface produces vibrations that can be converted intoelectrical energy. FIG. 1 is a graph 100 that illustrates theacceleration in tire rubber as the tire rolls at a specific speed, suchas 30 kilometers/hour. The accelerative force (in g's) along axis 102 isplotted against time (in seconds) 104 to A pressure sensor mountedwithin the tire, such as embedded within or coupled to the wheel or tirecarcass can be used to monitor the pressure inside the tire. For thisapplication, the use of a battery is impractical because the batterysize and weight may impact the tire balance, excessively cold or warmtemperatures within the tire can significantly affect batteryperformance, and replacement and disposal of the battery may beimpractical or costly. In one embodiment, a piezoelectric cantilever orbender structure is used to provide the requisite energy to the tirepressure sensor. The piezoelectric bender converts the accelerativeforces, such as those shown in FIG. 1, of the tire as it rolls intoelectricity for powering the pressure sensor.

In one embodiment, the energy harvesting device for use with a tirepressure sensor comprises a piezoelectric bender that includes apiezoelectric bimorph or multimorph structure. Piezoelectric materialsare materials that convert vibration energy into electric energy. Asingle piece of piezoelectric material by itself is generally a unimorphstructure that exhibits stress in equal and opposite directions undertransverse loading. Consequently, the output voltage will be zero in thecase of a sinusoidal vibration input. A bimorph structure has stress inone direction under a transverse load, and therefore outputs a non-zerovoltage under the application of sinusoidal vibration. To provideadequate power output in a wide variety of different vibratingenvironments, a bimorph structure is generally preferred.

FIG. 2A illustrates a piezoelectric bender for use in an energyharvesting device and utilizing a piezoelectric bimorph structure,according to an embodiment. The piezoelectric bender 200 consists of abase or housing 202, a piezoelectric element 206 attached to the plasticbacking 204, and a proof mass 208 attached to the piezoelectric element206. The proof mass could alternatively be attached to the plasticbacking 204. The piezoelectric element 206 and plastic backing piece 204together form the piezoelectric bimorph structure of the bender 200. Inan alternative embodiment, the bimorph strip can be implemented as apiezo/metal or piezo/piezo element, or a piezo stack comprising three ormore elements in a sandwich array. Such an array is referred to as a“multimorph” structure.

In one embodiment, the bimorph beam made up of 204 and 206 is integrallyformed as part of the base 202. This provides maximum rigidity of thebeam and base structure. When a vibration force is induced onto benderstructure 200, the bimorph beam consisting of backing 204 andpiezoelectric material 206 is deflected with a motion proportional tothe vibration force. This deflection is converted into electrical power,amplified, and then transmitted to other circuitry, such as that in asensor coupled to structure 200.

In one embodiment, the piezoelectric material is Lead Zirconate Titanate(PZT), such as a PZT-5A type ceramic, and the proof mass is Tungsten.The body 202 and backing material 204 can be made of ceramic or anysimilar inactive material, such as plastic, nylon, and so on. One ormore of the structures of FIG. 2A are formed by a print forming processin which the material is deposited in onto a surface in a series oflayering steps by a screen-printing or similar process. In general, thematerial is deposited in liquid or semi-liquid form and hardens to formthe final structure.

FIG. 2B illustrates the piezoelectric bimorph of FIG. 2A under atransverse loading input, such as the vibration illustrated in FIG. 1.As illustrated in FIG. 2B, the piezoelectric bender 200 bends from afirst position x₁ to a second position x₂, the amount of stress σproduced depends on the displacement of the proof mass from the firstposition to the second position. For an oscillating transverse input,such as a vibration, the piezo/plastic bimorph 210 will bend in thedirection corresponding to the phase of the vibration, thus producing apositive stress value dependent on the magnitude of displacement causedby the transverse load. The PZT material of the bimorph integrates thestress to produce a power output. The proof mass serves to increase thestress force since the force is proportional to the mass of the bimorphstrip and the induced acceleration.

In one embodiment, an energy harvesting device is made by a screenprinting process that encapsulates a bimorph or multimorph piezoelectricstrip within a miniaturized integrated package that can be deployed inmany different applications. FIG. 3 illustrates a cut-away view of anenergy harvesting device manufactured by a screen-printing process,according to an embodiment. As shown in FIG. 3, energy harvesting device300 consists of a piezoelectric bimorph or multimorph bender 302 (alsoreferred to as a “cantilever beam”) that is integrally connected to thebody 304 of the device. A rim structure 308 is integrally connected tothe package bottom 306 that forms the bottom of the device and surroundsthe piezo-electric bender 302 to provide the side structures and definethe body of the device. A lid 310 placed on top of the rim 308 coversthe piezoelectric bender 302 and seals the device 300. One or more vias312 are connected to a layer of the piezo-electric bender 302 to provideconductive connections to an electrical circuit coupled to the device300. The energy harvesting segment of device 300 is formed by thepiezoelectric bimorph cantilever beam 302 that vibrates under anexternally applied load. The cantilever is surrounded by an externalshell (package) made up of the package bottom 306, rim 308 and lid 310.The package surrounding the cantilever 302 provides the functions ofelectrical interconnect, environmental shielding, and over-travelprotection. The external package can be made of an electrically inertmaterial that is capable of hermetically sealing the cantilevered beam,such as ceramic or a dense composite, or similar material.

The energy harvesting device 300 including the cantilevered beam 302 andthe external package that encapsulates it, is formed by a screenprinting (print forming) process that involves laying down severalsuccessive layers of material. In one embodiment, the print formingprocess described utilizes the High-Volume Print Forming (HVPF™) processdeveloped by EoPlex Technologies, Inc. This is a print forming methodthat allows three-dimensional solid or hollow structures to be createdin a layered format using inorganic inks comprising ceramic and/or metalpowders. During the firing process, these powders retain their printedshape but sinter to high density. A “negative” ink or sacrificialmaterial is used to fill the areas where there is no positive ink toprovide a flat surface for the next layer. The sacrificial ink burns ormelts away during firing to create the desired cavities or channelswithin the structure. Other similar methods of screen printing thatresult in the build up of material on a base can also be used.

The external package consisting of at least one of the bottom 306, rim308 and lid 310 can be formed from the same screen printing process thatforms the cantilevered beam 302, or two or more different screenprinting processes can be used to form these different elements.

FIG. 4 is a flowchart that illustrates a method of manufacturing anencapsulated energy harvesting device, according to an embodiment. Instep 402 a carrier substrate is provided. This can be a ceramicsubstrate or similar material. Upon the carrier substrate is formed thebottom of the package and the surface mount pads, 404. Holes are formedor drilled into the layer forming the bottom of the package to allow forlater sacrificial material removal, 406. In step 408, the first part ofthe rim is printed around the device. Enough material should bedeposited to provide a structure that sufficiently separates thecantilever beam from the bottom plate. Vias are added to connect thesurface mount pads to the cantilever beam, step 410. The bottomelectrode is then printed and connected to one of the vias, 412. Ingeneral, the electrodes comprise the metal layer portion of thepiezoelectric bimorph. In step 414, the bottom layer of the cantileverbimorph is printed. This is an electrically inert (insulative) layermade by depositing the ceramic material of the housing. The middleelectrode of the piezoelectric bimorph is then printed and connected toa via, step 416. The top portion of the piezoelectric bimorph is printedin step 418. If the cantilever beam is a multimorph structure, multiplelayers of piezoelectric material and insulative materials can be laiddown. If a proof mass is to be used with the cantilever beam, it is canalso be formed beam structure by the same screen printing process. Instep 420, the upper electrode is printed and connected to acorresponding via. The upper part of the rim is then printed as is thelid, step 422. Once all of the layers have been printed, the device isfired to burn off the sacrificial materials (typically inks) and hardenthe ceramic and metal layers. The sacrificial material melts and flowsthrough the holes formed in step 406. Depending upon the type ofmaterials used, the firing process may instead be a curing process orany appropriate method of hardening the materials deposited by thescreen-printing steps. After firing or curing, the bimorph or multimorphis poled to make it piezoelectric if necessary. The device can then beconnected to or integrated with the electrical circuit for which it isto provide electrical power.

In one embodiment, the screen printing process that forms the packageand piezoelectric bimorph involves laying down successive layers ofdifferent materials embodied in ink or ink-like substances. Some of theink layers comprise the ceramic or similar material for the case, andothers comprise the metal layers for the cantilever and the vias, whilestill others are sacrificial inks to form the hollow areas of thedevice. Once all of the layers have been stacked and formed, the deviceconsisting of the case, the cantilever beam, the vias and the proof massare all formed as one unit. This structure is co-fired to remove thesacrificial material and harden the ceramic and metal material. Thisproduces the cavity around the cantilever and provides clearance when itvibrates.

FIGS. 5 through 11 illustrate the progression of manufacturing steps toproduce an energy harvesting device, such as that illustrated in FIG. 3and in accordance with the method described in the flowchart of FIG. 4.FIG. 5 illustrates a carrier or substrate 502 upon which a ceramicsubstrate 504 and surface mount pads 506 have been printed. Thesubstrate 502 can be a ceramic or similar inert material that providessufficient backing and support for the screen printing process that isused to form the device. The bottom plate 504 can be a ceramic materialor other material that is provided in a liquid or semi-liquid form fordeposition on the substrate through a screen printing process. Thematerial should be selected such that when dry, it is sufficiently hardand rigid to provide a solid structure for the vias 506, piezoelectriccantilever, and walls that will be formed thereon. Since the device is astructure that encloses a hollow cavity in which the cantilever isformed, several sacrificial layers are used to mask the ceramic andmetal inks during the screen printing process. The masked areasgenerally define the hollow or void areas within the device. In oneembodiment, flow holes 508 are formed in the bottom plate to allow theinks for the sacrificial layers to exit upon firing of the device.

The walls that form the sides of the device are formed by printing aceramic (or similar material) rim upon the bottom plate. FIG. 6illustrates the formation of walls 602 upon the substrate of FIG. 5. Asacrificial ink layer 601 is deposited on the bottom plate to define thecavity in which the cantilever beam is formed, and layers ceramic arebuilt up around this cavity to define the side walls of the device. Atthe same time, the two or more layers of the cantilever beam and thevias are formed. In one embodiment, the cantilever beam is a sandwichstructure of two or more electrode layers separated by inert ceramiclayers. Each electrode layer is a metal layer that is connected directlyto a corresponding via or formed as part of the same layer as the via,and each via is connected directly to a corresponding surface mount pad.As shown in FIG. 6, a first electrode layer 604 for the cantilever beamis formed by depositing the metal layer onto the sacrificial ink 601that forms the cavity of the device. To allow vertical movement of thebeam a sufficient gap should be provided between the first layer of thecantilever beam and the top surface of the bottom plate. The firstelectrode layer of the cantilever 604 is directly connected to via 606through conductive path 608. Electrode 604, via 606 and path 608 can allbe formed by the same screen printing step by depositing a metal layerin the appropriate pattern. In this same step, the remaining vias 610and 612 can be built-up.

After the first metal electrode layer is deposited a second ceramiclayer is deposited. This is illustrated in FIG. 7, which shows thedeposition of a ceramic layer of the cantilever beam of FIG. 6. Thisceramic layer adds an inert layer to the cantilever beam 702 and furtherbuilds up the walls 704. This layer also covers the first via 606 andtrace 608. A metal layer is deposited to build up the remaining vias 706and 708. FIG. 8 illustrates the formation of the second electrode on thecantilever beam of FIG. 7. As shown in FIG. 8, the second or middleelectrode 802 is formed by depositing a metal layer on the cantileverbeam and providing a trace 804 to the corresponding via 806. This metallayer also builds up remaining via 808. After the second electrode layeris printed, additional ceramic layers are printed to build up the walland provide the next ceramic layer for the cantilever beam. The third orupper electrode is then formed by depositing another metal layer.

FIG. 9 illustrates the formation of the third electrode on thecantilever beam of FIG. 8. As shown in FIG. 9, the third or upperelectrode 902 is formed by depositing a metal layer on the cantileverbeam and providing a trace 904 to the corresponding via 906. After thefinal electrode layer of the cantilever beam is printed, the wall isfurther built up to provide adequate top clearance for the verticalmovement (oscillation) of the beam and the attachment of any proof mass.FIG. 10 illustrates the deposition of rim layers 1004 and sacrificialink material 1002 over the cantilever beam of FIG. 9. The sacrificialink covers the beam structure and masks the ceramic layers that areprinted to further build up the rim wall 1004.

After a sufficient rim height is reaches, the device is enclosed byforming a lid that covers the cavity enclosing the cantilever beam. FIG.11 illustrates the formation of a lid on the rim structure of FIG. 10.In one embodiment, the lid 1002 is formed by depositing one or moreceramic layers on the previously formed rim walls by the same screenprinting process used to form the walls. Thus, as shown in FIG. 11, thelid 1002 is situated on the wall 1004 and together with bottom plate1006, fully encloses the cantilever beam formed within the device.Alternatively, the lid 1002 that covers the device can be formed as aseparate element that is glued or otherwise bonded onto the top surfaceof the rim wall 1004. The bottom plate has attached to it, or formedtherein surface mount pads that are directly connected to respectivevias to the corresponding electrodes of the cantilever beam.

In one embodiment, the piezoelectric material that is used to form theelectrodes of the cantilever beam is Lead Zirconate Titanate (PZT), suchas a PZT-5A type ceramic. Any similar material may be used, and suchmaterial is layered by the print forming method described above. Thematerial may be provided in the form of a paste (e.g., powder plusbinder) or liquid or semi-liquid form that is capable of being processedby the screen forming process. Depending upon the application of theenergy harvesting device, and the power output required, a proof massmay be attached to the cantilever beam to amplify the output energybased on the input force. In one embodiment, the proof mass is made of amaterial that can be co-fired with PZT, and is formed in layers by thesame print forming process used to form the cantilever beam and devicewalls.

Once the device is enclosed between the lid and bottom plate, as shownin FIG. 11, it is heated in a kiln or similar heating apparatus in afiring process. This process melts the sacrificial ink layers that exitthrough the holes formed in the bottom plate and leaves an open cavityaround the cantilever beam. The firing step also hardens the metal andceramic layers to that upon cooling a rigid assembly is produced. Theevacuation holes in the bottom plate can be filled in or capped if theunit is required to be fully sealed. One or more firing steps can beused depending upon the materials and physical characteristics of thedevice. If a single firing step is employed, the materials selected forthe metal and ceramic layers comprising the electrodes and wallsrespectively should be matched so that they harden at approximately thesame temperature. For example, the electrodes can be formed using SilverPalladium, while the case can be formed using Al₂O₃. Alternatively, amaterial such as Platinum can be used for both the electrodes and thecase.

Although embodiments have been directed to manufacturing an energyharvesting device using screen printing (print-forming) processes, itshould be understood that similar methods to form a device usingsuccessive layering of inks or material can also be used, such astape-up or similar processes.

As illustrated in FIG. 3, the resulting power harvesting device has apiezoelectric bimorph in the form of a cantilever beam that isintegrated directly with the body of the device. Through the successivelayering process that builds up both the walls of the device and theinert layers of the bimorph to sandwich the electrode layers, the beamis an extension of the body itself. As such, the device comprises aone-piece beam and case with very high rigidity.

The energy harvesting device described and illustrated with respect tothe embodiments of FIGS. 3 through 11 comprised a standalone powersupply device that can be coupled to one or more external circuits toprovide power for those circuits. In an alternative embodiment, passiveelectronic components can be integrated with the power harvesting deviceby forming these components in the same print forming manufacturingprocess. Such an integrated device can act as a self contained sensor orsimilar MEMS device. In one embodiment, the integrated energy harvestingdevice and sensor circuitry comprises a tire pressure monitoring system(TPMS) that is embedded in a tire or wheel, although other similarsensor applications in which a source of vibration energy is availableare also possible.

In one embodiment, a power harvesting device created by a print formingprocess, such as the EoPlex process (or a similar process) is createdwithin a case that forms part of the circuit substrate. FIG. 12Aillustrates an energy harvesting device with a proof mass formed withina case for integration with passive electronic components. Apiezoelectric bimorph 1204 forming a cantilever beam is formed from aceramic case 1202. One or more vias 1208 provide connection for theelectrical components that will be included in the device.

As shown in FIG. 12A, a proof mass 1206 is attached or formed as part ofthe bimorph cantilever 1204. As stated above, the proof mass may beformed in layers by the same print forming process used to form thecantilever beam and device walls (rim structure). FIGS. 12B through 12Dillustrate the formation of the proof mass and its integration with thecantilever beam, under an embodiment. As shown in FIG. 12B, the proofmass 1220 is formed within the rim structure 1222 by depositing layersof material through the print forming method. During the depositionstage, alternating layers corresponding to the electrode elements 1224of the piezoelectric beam are deposited, as shown in FIG. 12C; andalternating layers corresponding to the PZT elements 1226 of thepiezoelectric beam are deposited in between the electrode layers, asshown in FIG. 12D. In this manner, the proof mass is formed as anintegrated part of the piezoelectric beam. For an embodiment in whichthe energy harvesting device is produced by a firing process, the proofmass is made of a material that can be co-fired with the PZT material.For this embodiment, the proof mass itself is made of PZT, or aSilver/Palladium (Ag/Pd) alloy, or similar material. For an embodimentin which the device is not made by a firing process, a material such astungsten can be used.

In general, the energy harvesting device illustrated in FIG. 12A isformed by the print forming processes described above. Through thisprocess, a cap layer is also formed over the device, as described withreference to FIG. 11. In one embodiment, the cap layer of the energyharvesting device provides the substrate for the formation of additionalelectrical circuits. FIG. 13 illustrates the energy harvesting device ofFIG. 12A with a first layer of passive components. The cap layer 1308 isformed on the case 1310. On this layer are formed additional components,such as capacitor plate 1304, vias 1306 and spiral inductor 1302. Thislayer could contain any combination of inductors, capacitors, orinterconnection structures. An interlayer ceramic layer is then printedover the first component layer. This layer should have propertiesdesigned to improve the performance of the passive elements, such as ahigh dielectric constant, magnetic permeability, and so on. A secondlayer of passive components is then printed. FIG. 14 illustrates theenergy harvesting device of FIG. 13 with a first layer of passivecomponents. On layer 1402, a second capacitor plate 1406 is formed alongwith spiral inductor 1404 and vias 1408. Another ceramic interlayer isprinted on top of this component layer, and then a top layer structureis printed on this ceramic interlayer. The top layer structure cancontain bond pads and additional passive elements. FIG. 15 illustratesthe energy harvesting device of FIG. 14 with a top layer of surfacemount electrical components 1502. The finished structure is then firedand the piezo material is polarized.

Depending upon the application of the circuit and power harvestingcircuit, additional components, such as integrated circuit elements(MEMS and ASICS) can be solder bonded via a flip chip process, orsimilar method, to the substrate. The system can then be placed inside aplastic housing and embedded in the tire or whatever environment thecircuit is to be deployed. FIG. 16 illustrates a power harvesting deviceand sensor/transmitter circuit of an intelligent tire system, under anembodiment. The integrated power harvesting/component circuit 1602 isencased within plastic housing 1604. For a tire pressure sensingapplication, a channel 1606 is provided to enable pressure to bemeasured by the circuit.

The passive electrical components formed in the interlayer regions ofthe device illustrated in FIGS. 12 through 16 are formed by a printforming process similar or identical to that used to produce the energyharvesting portion of the device. The components placed on the top layerstructure can be active semiconductor devices that are soldered onto thetop layer, or they could be additional passive components eithersoldered to the top layer or formed by an additional print forming step.The integrated device, such as device 1602 of FIG. 16 eliminates theneed to use a printed circuit board based circuit in conjunction withthe energy harvesting device 1202.

Although embodiments have been described in relation to a tire pressuresensor system, it should be understood that these or similarembodiments, can be utilized with respect to a wide variety of othermicrosystems involving sensors or devices that require and can operateat relatively low power. These include motion sensors, infrared sensors,leak detectors, lubricant monitors, and other applications that have acharacteristic that can be measured and feature a vibrating environment.For example, sensors using a piezoelectric bender for electrical powercan be mounted within a vehicle fuel tank to monitor fuel quantity orquality, or within an engine crankcase to monitor oil quantity andquality. Embodiments of the energy harvesting device can be applied tomany different industries, such as automotive or aerospace applications,industrial machinery, seismic applications, and oceanographicapplications, among others.

The sensors used in conjunction with the energy harvesting device can beequipped with any suitable sensing and transmission circuitry, such asRF, microwave, or similar wireless communication means. Alternatively,some applications may be suitable for wired sensor communication.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in a sense of “including,but not limited to.” Words using the singular or plural number alsoinclude the plural or singular number respectively. Additionally, thewords “herein,” “hereunder,” “above,” “below,” and words of similarimport refer to this application as a whole and not to any particularportions of this application. When the word “or” is used in reference toa list of two or more items, that word covers all of the followinginterpretations of the word: any of the items in the list, all of theitems in the list and any combination of the items in the list.

The above description of illustrated embodiments of the energyharvesting device for use with microsystem sensors is not intended to beexhaustive or to limit the embodiments to the precise form orinstructions disclosed. While specific embodiments of, and examples for,the energy harvesting device are described herein for illustrativepurposes, various equivalent modifications are possible within the scopeof the described embodiments, as those skilled in the relevant art willrecognize.

The elements and acts of the various embodiments described above can becombined to provide further embodiments. These and other changes can bemade to the energy harvesting device in light of the above detaileddescription.

In general, in the following claims, the terms used should not beconstrued to limit the described system to the specific embodimentsdisclosed in the specification and the claims, but should be construedto include all operations or processes that operate under the claims.Accordingly, the described system is not limited by the disclosure, butinstead the scope of the recited method is to be determined entirely bythe claims.

While certain aspects of the energy harvesting device are presentedbelow in certain claim forms, the inventor contemplates the variousaspects of the methodology in any number of claim forms. Accordingly,the inventor reserves the right to add additional claims after filingthe application to pursue such additional claim forms for other aspectsof the described system.

1. A device comprising: a housing including a bottom portion and a rimportion integrally formed around a perimeter of the bottom portion, thebottom portion including one or more holes to allow drainage ofsacrificial material during a print forming process employed duringmanufacture of the device; a substrate strip constituting part of acantilever beam formed from the rim portion and protruding over an areaof the bottom portion; first conductive layer laid on top of thesubstrate strip; an inert layer laid on top of the first conductivelayer; a second conductive layer laid on top of the inert layer; a firstvia formed within the rim portion and coupled to the first conductivelayer; a second via formed within the rim portion and coupled to thesecond conductive layer; a proof mass attached to the cantilever beam; avoid area separating the cantilever beam from the bottom portion, thevoid area configured to allow at least one end of the cantilever beam tomove vertically relative to the bottom portion in response to movementof the device, the void area formed by drainage of the sacrificialmaterial through the holes during the print forming process: a lidplaced on a top area of the rim portion to seal the cantilever beamwithin the void area; a first surface mount pad on a surface of the lidand coupled to the first via; and a second surface mount pad on thesurface of the lid and coupled to the second via.
 2. The device of claim1, wherein the first and second conductive layers each comprises apiezoelectric material.
 3. The device of claim 2, wherein thepiezoelectric material comprises Lead Zirconate Titanate (PZT) and eachof the bottom portion, rim portion and lid comprises a ceramic material.4. The device of claim 3 further comprising one or more passiveelectronic elements integrated within the case and deposited onto thesurface of the lid by the print forming process.
 5. The device of claim1 wherein each via and conductive layer is formed by depositing a metallayer during the print forming process.
 6. The device of claim 1 whereinthe cantilever beam is configured to deflect in a directioncorresponding to a vibration force induced onto the proof mass andgenerate an electric current in response to the vibration force.
 7. Thedevice of claim 6, wherein the electric current is provided to a sensordevice mounted in a system containing the device to provide operatingpower to the sensor device.
 8. An energy harvesting device comprising: acase made of a hardened ceramic material, the case comprising a wallstructure and a bottom portion encompassing a cavity, the bottom portionincluding one or more holes to allow drainage of sacrificial materialduring a print forming process employed during manufacture of thedevice; a piezoelectric cantilever beam disposed within the cavity andintegrally formed as part of the wall structure, the piezoelectriccantilever beam comprising at least two conductive layers separated byan inert layer; a first via within the wall structure coupled to thefirst conductive layer of the at least two conductive layers; a secondvia within the wall structure coupled to the second conductive layer ofthe at least two conductive layers; a lid placed on a top area of thewall structure to seal the piezoelectric cantilever beam within thecavity, wherein a portion of the cavity separates the piezoelectriccantilever beam from the bottom portion, and is configured to allow atleast one end of the piezoelectric cantilever beam to move verticallyrelative to the bottom portion in response to movement of the device,the cavity formed by drainage of the sacrificial material through theholes during the print forming process: a first surface mount pad on asurface of the lid and coupled to the first via; and a second surfacemount pad on the surface of the lid and coupled to the second via. 9.The device of claim 8, wherein the case and piezoelectric cantileverbeam and lid are formed by a print forming process consisting ofprinting successive layers of ceramic material and metal material on asubstrate.
 10. The device of claim 9, wherein the wherein thesacrificial material comprises an ink.
 11. The device of claim 10,further comprising the step of forming a proof mass through the printforming method such that it forms an integral part of the piezoelectriccantilever beam.
 12. The device of claim 10 wherein the piezo bimorphstrip is configured to deflect within the cavity and in a directioncorresponding to a vibration force induced onto the proof mass andgenerate an electric current in response to the vibration force toprovide operating power to a circuit coupled to the device.
 13. Thedevice of claim 12, wherein the piezoelectric material comprises LeadZirconate Titanate (PZT), and the proof mass comprises one of PZT andsilver/palladium alloy.
 14. The device of claim 10, further comprisingone or more passive electronic elements integrated within the case anddeposited onto the case by the print forming process.
 15. The device ofclaim 9, wherein the device comprises part of a power circuit for an airpressure sensor.
 16. The device of claim 15, wherein the air pressuresensor and power circuit are mounted inside the tire of a vehicle.
 17. Amethod of producing a device comprising: depositing a layer of ceramicmaterial through a screen printing process on a substrate to form abottom plate; depositing a neutral ink on a portion of the bottom plateto define a cavity; depositing successive layers of ceramic material ontop of the bottom plate to define a wall structure around the portion ofthe bottom plate defining the cavity; depositing layers of ceramicmaterial interspersed with metal layers within the portion defining thecavity to form a cantilever beam within the cavity; depositing a toplayer on an upper surface of the wall structure to form a lid sealingthe cavity; firing the device to remove the neutral ink and harden theceramic material and metal layers.
 18. The method of claim 17 furthercomprising the step of forming a one or more evacuation holes in thebottom plate to facilitate removal of the neutral ink during the firingstep.
 19. The method of claim 17, further comprising printing one ormore successive layers of interspersed neutral ceramic layers and metallayers to define one or more passive electrical components on the toplayer of the device.
 20. The method of claim 19, further comprising thestep of encasing the device in a plastic housing.